[89.06] Ultraviolet Imaging of Starburst Rings in Disk Galaxies at Low and High Redshift

Imaging in the restframe ultraviolet has proven to be an
effective and vital means of tracing starbirth activity in
galaxies out to high redshifts. Using images from the
Ultraviolet Imaging Telescope (UIT), Hubble Space Telescope
(HST), and complementary optical telescopes, we have
investigated the starburst activity and associated dynamics
in nearby ringed disk galaxies. Concentrating on the
Sab-type starburst-ring galaxy M94 (NGC 4736), we find that
most of the star formation is being orchestrated via a
nuclear mini-bar/inner-ring/oval-disk/outer-ring dynamic.
The inner starburst ring and bi-symmetric knots at
intermediate radius, in particular, argue for bar-mediated
resonances as the primary drivers of evolution in M94 at
the present epoch. Similar ring-bar dynamics may prevail
in the centers of the ``core-halo'' galaxies that
have been marginally resolved at high redshift. The
gravitationally lensed ``Pretzel Galaxy'' (0024+1654) at
a redshift of \sim2 provides an important precedent in
this regard, wherein reconstructions of the galaxy's
emitting structure clearly show an annular morphology in
the restframe UV.
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